The concept of derivatizing V.I. improving high molecular weight ethylene copolymers, with acid moieties such as maleic anhydride, followed by reaction with an amine to form a V.I.-dispersant oil additive is known as indicated by the following patents.
U.S. Pat. No. 3,316,177 teaches ethylene-propylene-diene, which are heated to elevated temperatures in the presence of oxygen so as to oxidize the polymer and cause its reaction with maleic anhydride which is present during the oxidation. The resulting polymer can then be reacted with alkylene polyamines.
U.S. Pat. No. 4,089,794 teaches grafting the ethylene copolymer with maleic anhydride using peroxide in a lubricating oil solution, wherein the grafting is preferably carried out under nitrogen, followed by reaction with polyamine.
U.S. Pat. No. 4,137,185 teaches reacting C.sub.1 to C.sub.30 monocarboxylic acid anhydrides, and dicarboxylic anhydrides, such as acetic anhydride, succinic anhydride, etc. with an ethylene copolymer reacted with maleic anhydride and a polyalkylene polyamine to inhibit cross linking and viscosity increase due to further reaction of any primary amine groups which were initially unreacted.
U.S. Pat. No. 4,144,181 is similar to 4,137,185 in that it teaches using a sulfonic acid to inactivate the remaining primary amine groups when a maleic anhydride grafted ethylene-propylene copolymer is reacted with a polyamine.
U.S. Pat. No. 4,169,063 reacts an ethylene copolymer in the absence of oxygen and chlorine at temperatures of 150.degree. to 250.degree. C. with maleic anhydride followed by reaction with polyamine.
A number of prior disclosures teach avoiding the use of polyamine having two primary amine groups to thereby reduce cross-linking problems which become more of a problem as the number of amine moieties added to the polymer molecule is increased in order to increase dispersancy.
German Published Application No. P3025274.5 teaches an ethylene copolymer reacted with maleic anhydride in oil using a long chain alkyl hetero or oxygen-containing amine.
U.S. Pat. No. 4,132,661 grafts ethylene copolymer, using peroxide and/or air blowing, with maleic anhydride and then reacts with a primary-tertiary diamine.
U.S. Pat. No. 4,160,739 teaches an ethylene copolymer which is grafted, using a free-radical technique, with alternating maleic anhydride and a second polymerizable monomer such as methacrylic acid, which materials are reacted with an amine having a single primary, or a single secondary, amine group.
U.S. Pat. No. 4,171,273 reacts an ethylene copolymer with maleic anhydride in the presence of a free-radical initiator and then with mixtures of C.sub.4 to C.sub.12 n-alcohol and amine such as N-aminopropylmorpholine or dimethylamino propyl amine to form a V.I.-dispersant pour depressant additive.
U.S. Pat. No. 4,219,432 teaches maleic anhydride grafted ethylene copolymer reacted with a mixture of an amine having only one primary group together with a second amine having two or more primary groups.
German published application No. 2753569.9 shows an ethylene copolymer reacted with maleic anhydride by a free-radical technique and then reacted with an amine having a single primary group.
German published application No. 2845288 grafts maleic anhydride on an ethylene-propylene copolymer by thermal grafting at high temperatures and then reacts with amine having one primary group.
French published application No. 2423530 teaches the thermal reaction of an ethylene copolymer with maleic anhydride at 150.degree. C. to 210.degree. C. followed by reaction with an amine having one primary or secondary group.
The early patents such as U.S. Pat. Nos. 3,316,177 and 3,326,804 taught the general concept of grafting an ethylene-propylene copolymer with maleic anhydride and then reacting with a polyalkylene polyamine such as polyethylene amines. Subsequently, U.S. Pat. No. 4,089,794 was directed to using an oil solution for free radical peroxide grafting the ethylene copolymer with maleic anhydride and then reacting with the polyamine. This concept had the advantage that by using oil, the entire reaction could be carried out in an oil solution to form an oil concentrate, which is the commercial form in which such additives are sold. This was an advantage over using a volatile solvent for the reactions, which has to be subsequently removed and replaced by oil to form a concentrate. Subsequently, in operating at higher polyamine levels in order to further increase the dispersing effect, increased problems occurred with the unreacted amine groups cross-linking and thereby causing viscosity increase of the oil concentrate during storage and subsequent formation of haze and in some instances gelling. Even though one or more moles of the ethylene polyamine was used per mole of maleic anhydride during imide formation, cross-linking became more of a problem as the nitrogen content of the polymers was increased. One solution was to use the polyamines and then to react the remaining primary amino groups with an acid anhydride, preferably acetic anhydride, of U.S. Pat. No. 4,137,185 or the sulfonic acid or U.S. Pat. No. 4,144,181. The cross-linking problem could also be minimized by avoidance of the ethylene polyamines and instead using amines having one primary group which would react with the maleic anhydride while the other amino groups would be tertiary groups which were substantially unreactive. Patents or published applications showing the use of such primary-tertiary amines noted above are U.S. Pat. No. 4,219,432, wherein a part of the polyamine was replaced with a primary-tertiary amine; U.S. Pat. No. 4,132,661; U.S. Pat. No. 4,160,739; U.S. Pat. No. 4,171,273; German No. P2753569.9; German No. 2,845,288; and French No. 2,423,530.
Moreover, oleaginous compositions, particularly concentrates, of some of these nitrogen containing grafted olefin polymers, particularly those containing an unreacted primary amino group, tend to exhibit an increase in viscosity over a period of time. The source of the viscosity increase over an extended period of time of oil solutions of these additives appears to be, at least in part, due to the chain extension of the polymer. Several solutions to this problem are described in the prior disclosures. One solution is to use the polyamines and then to react the remaining unreacted primary amino groups with acid anhydrides of either C.sub.1 -C.sub.30 monocarboxylic acids, preferably acetic anhydride, or unsubstituted or C.sub.1 to C.sub.8 hydrocarbyl substituted dicarboxylic acid anhydrides of U.S. Pat. No. 4,137,185; or the sulfonic acids of U.S. Pat. No. 4,144,181. Those materials act as polyamine group end-capping or inactivating agents to inhibit or limit chain extension. That is to say, the reaction product of the graft copolymer of the ethylenically unsaturated dicarboxylic acid material and polyamine is post-treated with these acid materials to inhibit chain extension and, therefore, viscosity increase of the imide grafted ethylene copolymer.
While the end-capping or amine inactivating agents disclosed in U.S. Pat. Nos. 4,137,185 and 4,144,181 are generally quite useful, their utilization results in some problems under certain conditions. Thus, for example, reacting a monocarboxylic acid anhydride, e.g., acetic anhydride, with the polyamine yields an acid byproduct, e.g., acetic acid. This acid is deleterious to engine operation, causing corrosion, and generally needs to be removed from the oil solution of the V. I. improver - dispersant. Furthermore, the use of the unsubstituted or lower hydrocarbyl substituted dicarboxylic acid anhydrides of U.S. Pat. No. 4,137,185 generally does not remedy, and may sometimes even contribute to, the formation of haze in oil solutions of the imide grafted ethylene copolymer. This is due to the fact that when using free radical initiators with mineral oil as the grafting medium a proportion of the oil molecules in turn become grafted with the ethylenically unsaturated moiety, e.g., maleic anhydride, and upon subsequent reaction with the amine these grafted oil particles tend to become insoluble and to form haze. Upon the addition of the hydrocarbyl substituted dicarboxylic acid anhydrides to this oil solution to inactivate the unreacted primary amine groups of the imide grafted ethylene copolymer, a certain proportion of the anhydride reacts with the free amine groups of the grafted oil particles. Since the prior disclosure anhydrides are either unsubstituted or lower hydrocarbyl substituted they do not facilitate the solubilization of these insoluble grafted oil particles. However, since the dicarboxylic acid anhydrides of the instant invention are substituted with a C.sub.12 to C.sub.18 hydrocarbyl group they tend to facilitate the solubilization of the insoluble grafted oil particles, thereby decreasing haze.
The use of the sulfonic acids of U.S. Pat. No. 4,144,181 may also result in the formation of undesirable acid by-products, e.g., hydrogen sulfide.
Furthermore, these prior disclosure end-capping or primary amine inactivating agents do not, in all instances, provide a sufficient degree of viscosity stability for some applications to oil solutions of the additives of this invention.
U.S. Pat. No. 4,803,003 discloses the use of a C.sub.12 -C.sub.18 hydrocarbyl substituted dicarboxylic acid anhydride to end-cap or react with any remaining primary amino groups of acid grafted ethylene copolymer reacted with polyamines containing at least two primary amino groups, thereby improving the viscosity stability of oil solutions of said nitrogen containing acid material grafted ethylene copolymer. However, the polyamine reactants disclosed in this patent are not the amido amine or thioamido amine reactants of the instant invention.
U.S. Pat. No. 4,517,104 discloses polymeric viscosity index (V.I.) improver-dispersant additive for petroleum oils, particularly lubricating oils, comprising a copolymer of ethylene with one or more C.sub.3 to C.sub.28 alpha-olefins, preferably propylene, which has been grafted with acid moieties such as maleic anhydride using a free radical initiator in a solvent such as lubricating oil, and then reacted with a carboxylic acid component including hydrocarbyl substituted succinic anhydride or acid having 12-400 carbon atoms in said hydrocarbyl group or long chain monocarboxylic acid, and a polyamine having two or more primary amine groups. Or the grafted polymer may be reacted with said acid component prereacted with said polyamine to form salts, amides, imides, etc. and then reacted with said grafted olefin polymer. These reactions can permit the incorporation of varnish inhibition and dispersancy into the ethylene copolymer while inhibiting cross-linking or gelling.
U.S. Pat. No. 4,632,769 discloses oil soluble viscosity index improving ethylene copolymers, such as copolymers of ethylene and propylene, reacted or grafted with ethylenically unsaturated carboxylic acid moieties, preferably maleic anhydride moieties, and then reacted with polyamines having two or more primary amine groups and a C.sub.22 to C.sub.28 olefin carboxylic acid component. These reactions can permit the incorporation of varnish inhibition and dispersancy into the ethylene copolymer while inhibiting cross-linking or gelling.
U.S. Pat. No. 2,921,085 relates to the preparation of beta-aminopropionamides by reaction of an alkyl amine with an acrylate to form an alkyl aminopropionate and reaction of the latter compound with an amine. The resulting compounds are disclosed to have utility as surface active agents, specifically as emulsifying, wetting, foaming and detergent agents.
U.S. Pat. No. 3,337,609 relates to adducts of hydroxyalkyl alkylene polyamines and acrylates. The resulting adducts are added to polyepoxides to provide compositions which are suitable for use as a barrier coating for polyethylene surfaces, and for additional end uses, such as in molding. In addition, the adducts are disclosed to be useful as catalysts in resin preparation and as corrosion inhibitors in water systems for ferrous metals.
U.S. Pat. No. 3,417,140 relates to the preparation of amido-amine compositions, which are useful as epoxy resin curing agents, by reacting a polyalkylene polyamine and a fatty amine (comprising a mono- or diamine having as one of the substituents on a nitrogen atom a hydrocarbyl radical having 8 to 24 carbon atoms) with an alpha-beta unsaturated carbonylic compound. It is disclosed that this reaction occurs through the Michael addition of an amine group across the unsaturated group of the carbonylic compound and through the condensation of an amine group with the carbonylic group.
U.S. Pat. No. 3,247,163 also relates to curing agents for polyepoxide compositions, which curing agents are prepared by reacting an organic amine and an acrylate.
U.S. Pat. No. 3,445,441 relates to amino-amido polymers characterized by being a reaction product of at least a polyamine and an acrylate type compound, such as methyl or ethyl acrylate, and methyl or ethyl methacrylate. The patent states that the polymers are useful in a wide variety of applications, such as floculating agents, water clarifying additives, corrosion inhibitors in oil and gas wells, and as lube oil additives. The patent further discloses that the polymers may be derivitized, including acylation with monocarboxylic acids and polycarboxylic acids, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, for example, diglycolic, phthalic, succinic, etc., acids.
U.S. Pat. No. 3,903,003 relates to lubricating compositions containing an amido-amine reaction product of a terminally carboxylated isoprene polymer which is formed by reacting a terminally carboxylated substantially completely hydrogenated polyisoprene having an average molecular weight between about 20,000 and 250,000 and a nitrogen compound of the group consisting of polyalkylene amines and hydroxyl polyalkylene amines.
U.S. Pat. No. 4,493,771 relates to scale inhibiting with compounds containing quaternary ammonium and methylene phosphonic acid groups. These compounds are derivatives of polyamines in which the amine hydrogens have been substituted with both methylene phosphonic acid groups or their salts and hydroxypropyl quaternary ammonium halide groups. The patent discloses that any amine that contains reactive amino hydrogens can be utilized, for example, polyglycol amines, amido-amines, oxyacylated amines, and others.
U.S. Pat. No. 4,459,241 contains a similar disclosure to U.S Pat. No. 4,493,771.
The materials of the present invention are an improvement over those of the aforediscussed prior disclosures because of their effectiveness and their ability to provide enhanced lubricating oil dispersancy, and because oleaginous compositions, particularly oil concentrates, containing these materials exhibit viscosity stability over time, e.g., upon storage.